Furnace conveyor system

ABSTRACT

A resilient gear system especially adapted for use with hightemperature furnaces and operative to provide positive and continuous transport of a work product through a furnace. A pair of counterrotating resilient gears are disposed at the entrance end of a furnace and are cooperative with serrated side surfaces of product carriers to effectively mate with the carriers in gear-coupled relationship for positive transport of the carriers through the furnace.

United States Patent Inventor Jacob Howard Beck Waban, Mass.

Appl. No. 21,302

Filed Mar. 20, 1970 Patented Oct. 5, 1971 Assignee BTU Engineering Corporation Waltham, Mass.

FURNACE CONVEYOR SYSTEM 5 Claims, 3 Drawing Figs.

US. Cl 198/1, 198/167, 214/18 R Int. Cl B65g 19/00 Field of Search 198/167, 1,

[56] References Cited UNITED STATES PATENTS 2,737,284 3/1956 Ball 198/9 3,417,851 12/1968 Gonski et al 198/9 FOREIGN PATENTS 81,039 11/1952 Norway 198/167 Primary Examiner-Richard E. Aegerter Assistant Examiner-Douglas D. Watts Attorney-Joseph Weingarten ABSTRACT: A resilient gear system especially adapted for use with high-temperature furnaces and operative to provide positive and continuous transport of a work product through a furnace. A pair of counterrotating resilient gears are disposed at the entrance end of a furnace and are cooperative with serrated side surfaces of product carriers to effectively mate with the carriers in gear-coupled relationship for positive transport of the carriers through the furnace.

PATENTEUUET sum -3.'610.391

INVENTOR J. HOWARD BECK BY Q l a fxwoaw YS FURNACE CONVEYOR SYSTEM FIELD OF THE INVENTION This invention relates to conveyor furnaces and more particularly to an external conveyor system for the efficient transport of a work product through a high-temperature precision furnace.

BACKGROUND OF THE INVENTION Conveyor furnaces are often employed in the heat processing of materials. Such furnaces generally include an elongated fumace muffle which may be divided into separate zones of independently controlled temperature and gas environment to suit particular heat processes. The work product is usually conveyed through the furnace by means of a woven metal belt moved along the furnace hearth and supported therein by a metal-supporting structure. At temperatures generally above l,l C., such as required for the sintering of powder metals, nuclear fuels and the firing of ferrites and titinates, such conveyor belts and their supporting structures cannot practically be employed as the metal will soften or melt at these elevated temperatures. In addition, even at lower temperatures at which the metal retains its integrity, such belts are often a source of contamination by reason of outgassing and oxidation, with a result that a clean furnace environment is difficult to maintain.

The construction of furnaces for use at temperatures above which metal conveyor belts are usable have conventionally employed push rod systems in which a row of product carriers are conveyed through the furnace by means of a push rod located at the entrance end of the furnace. The push rod can be for example a reciprocating hydraulic cylinder disposed in line with the furnace chamber and arranged to drive a row of I product carriers therethrough. The push rod structure is generally cumbersome and is disposed in a position which can often interfere with the efficient supply of product carriers to the furnace. Moreover, such push rod apparatus provides only incremental movement of the product carriers, and, especially at higher temperatures, the carriers can stick to the supporting furnace surface.

SUMMARY OF THE INVENTION In accordance with the present invention, a continuous conveyor system is provided which is especially adapted for use with high-temperature heat-treating furnaces and which transports a work product through the furnace in a positive, nonslipping manner and in a manner which aids in efficient heat processing of the product. A pair of counterrotating resilient gears are provided at the entrance end of a furnace and cooperate with serrated sides of product carriers to propel the carriers without slippage through the furnace. The resilient gears each include a multitooth rigid inner gear having a resilient tire formed therearound and operative to mate with the serrations of the product carriers without material deformation. The tire extrudes into the associated serrations on the product carrier to effectively provide a mating gear which is in intimate contact with the carrier. The resilient gears are continuously rotating and therefore provide continuous movement of the product carriers through the furnace. Since the product carriers are in continuous motion, there is little tendency for the carriers to fuse or stick to the supporting furnace hearth, as in conventional push rod systems.

The resilient gears and the driven product carriers are in gear-coupling relationship with one another and a positive driving force is thereby imparted to the carriers. There is substantially no slippage between the product carrier and the driving gears, even under the load of a row of many carriers, and as a result, the time cycle of the work product through the furnace is precisely maintained. The novel conveyor system permits the efficient supply of product carriers to the furnace, which can be accomplished, for example by an inclined roller track to guide carriers into driven relation with the resilient conveyor gears. A work product need not be supplied to the novel conveyor system in a time sequential manner, as in conventional push rod systems. Rather, the invention provides continuous transport of a work product through a furnace, and a supply row of product carriers can simply be maintained at the furnace entrance to feed carriers to the novel conveyor.

DESCRIPTION OF THE DRAWINGS The'invention will be more fully' understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partly cutaway pictorial view of a conveyor system according to the invention;

FIG. 2 is a partly cutaway top view of the invention; and

FIG. 3 is a cutaway pictorial view of an alternative embodiment of a resilient gear conveyor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION I A rotary conveyor system according to the invention for providing continuous and positive transport of product carriers through a heat-treating furnace is illustrated in FIGS. 1 and 2. Referring to the drawings, there is shown the entrance end of a furnace which includes an elongated chamber 10 typically formed of a high-temperature ceramic material such as alumina, and supported within insulating fire brick 12. As is well known, the furnace chamber and its surrounding insulating fire brick is usually contained within a metal housing, and suitable heaters provided within the furnace for requisite heating of a work product being conveyed therethrough. The furnace may be divided into respective zones along the length thereof, each zone being individually controlled as to its gaseous environment and operating temperature. In this manner a work product can be conveyed through a furnace having a predetermined temperature and gas profile to accomplish specific heat processes.

A work product is conveyed through the furnace on product carriers 14 which in the illustrated embodiment are of tray configuration. Product carriers 14 are formed of a high temperature material such as alumina capable of withstanding the operating temperatures within the furnace and which also are substantially nonreacting with the work product being processed. The product carriers are supported within the furnace on a hearth 20 which includes raised shoulders 21 on each side thereof to maintain alignment of the carriers in their travel through the furnace. A channel 16, which may include a plurality of transversely extending rollers 18, is disposed as an extension of hearth 20 for the support of carriers 14 being driven into the furnace. The product carriers 14 are supplied to the supporting channel 16 by means of an inclined roller track 22 arranged, as illustrated, as an extension of support 16.

The rotary conveyor drive embodying the invention includes first and second counterrotatable resilient gears 24 and 26, each of which is disposed on a respective opposite side of support channel 16 and each of which is adapted to engage in gear-coupling relationship a confronting grooved side of a product carrier 14 disposed therebetween. The sides of product carriers 14 which confront the resilient gears 24 and 26 have serrations or grooves 28 vertically formed therein in a regular array and-extending substantially along the full length of the carrier sides. Each resilient gear 24 and 26 includes an inner rigid gear 30, typically formed of metal, and a surrounding resilient tire 32, formed for example of silicone, which is molded or otherwise formed around inner rigid gear 30 with the tire being in intimate contact with the surfaces of gear teeth 31. Each resilient gear 24 and 26 is secured to and is rotatable with a respective shaft 34 and 36 which, in turn, is secured to a respective driving gear 38 and 40. Gear shafts 34 and 36 are for example rotatably disposed within a suitable bearing structure provided in support plate 42.

As seen more clearly in FIG. 2, driving gears 38 and 40 are in meshing relationship and are driven by any suitable motive means (not shown). In practice, the product carriers 14 are conveyed through the furnace at a relatively slow rate, typically 1-2 inches per minute; accordingly, the rotational velocity of resilient gears 24 and 26 is extremely slow, of the order of 0.1 revolutions per minute. Such slow speed rotary power is typically provided by means of a gear train driven by an electric motor. Driving gears 38 and 40 are of the involute type which can remain in mesh over a predetermined variation in distance between gear centers. This feature of involute gears can be utilized in the invention to provide positive and synchronous driving of the counterrotating resilient gears 24 and 26 even in the presence of variations in the width of product carriers 14 being driven or in the depth of serrations 28. To provide such variable meshing, gears 38 and 40 would of course be adjustably mounted to permit movement between gear centers.

The resilient tires 32 of gears 24 and 26 engage the respective serrated sides of the product carrier 14 disposed therebetween, the tires being employed within their elastic limit such that gear teeth are effectively formed in the region of contact with the associated serrations 28. An adaptive gear is thereby formed which can accommodate for variations in the depth or width of the serrations 28 to prbvide positive transport of product carriers through the furnace. In operation, each product carrier is conveyed down inclined track 22 into engagement with the counterrotating resilient gears 24 and 26. The resilient gears engage the respective serrated sides of carriers 14 with sufficient force to cause formation of gear teeth in tires 32 which conform exactly with the grooved surfaces of the carrier and which mate therewith in positive gear-coupling relationship. The driven product carrier pushes the row of carriers preceding it through the furnace, the carriers at the exit end of the furnace being removed therefrom by a suitable conveyor mechanism such as an inclined chute or roller conveyor.

It is a particular feature of the invention that each resilient tire 32 is formed around its respective inner gear wheel 30 in a manner which relieves the compressional force experienced by tires 32 when engaging the product carrier 14. The inner gear 30 provides a large area convoluted surface for securing tire 32 thereon, and additionally provides areas within tire 32 for stress relief as the resilient gear engages a product carrier. The depth of the resilient tire 32 in the region between gear teeth 31 of rigid gear 30 is greater than the depth of the tire in the region above the gear teeth. As a result, pressure applied to the contact area of the tire perimeter, as caused during engagement of the product carriers, tends to be relieved into this elastic region of greater depth, thereby minimizing deformation of the tire as it rotates in gear-coupling relationship with the product carriers. The resilient gears 24 and 26 are further maintained in a substantially nondeformed circular configuration by "means of rollers 44 disposed in rolling contact with respective gears 24 and 26 at positions, as illustrated, near the contact area of the respective gears and rearward of the contact area. The rollers 44 are operative to rotate with respective gears 24 and 26 and to maintain the peripheral configuration of resilient tires 32 to further lessen any tendency of the elastic material to flow or bulge as the resilient gears rotate in driving engagement with carriers 14.

An alternative means of moving the driving gears in a substantially nondeformed condition is illustrated in FIG. 3. The resilient gears, only gear 26 of which is illustrated in FIG. 3, are rotatably disposed within an encircling band 46 which extends around the periphery of the resilient gear except for the portion thereof in contact with the serrated side surface of a product carrier 14. The encircling band 46 includes end portions 48 which flair outwardly from the peripheral surface of the resilient gear to avoid possible abrasion of the tire by the ends of the band.

The invention provides continuous and positive conveyance of product carriers through the furnace by virtue of the effective resilient gearing arrangement described above. There is substantially no slippage between the resilient gears and the product carriers being conveyed, and, as a result, the time cycle of a work product through the furnace is precisely maintained. It should be noted that the resilient driving wheels do not engage the confronting surfaces of the product carriers merely by friction contact, but rather engage the serrated confronting surfaces of the product carriers effectively in gearcoupling relationship. As discussed, the product carriers are usually moved through the furnace at a relatively slow rate and it is especially important that a positive driving force be applied to the carriers to assure uniform and continuous motion through the furnace. Typically, a heat-treating furnace may be several feet long and a row of several product carriers are simultaneously being driven through the furnace. By virtue of the invention, a positive and continuous driving force is provided even for a relatively heavy row of carriers. Moreover, the invention allows for efiicient supply of product carriers to the furnace. As described, product carriers are simply queued up at the furnace entrance and are transported successively into the furnace by operation of the novel rotary conveyor system.

As an example of a rotary conveyor system embodying the invention, resilient gears 24 and 26 can be 5 inches in diameter, with rigid inner gears 30 being 4 inches in diameter and having 48 teeth. The product carriers 14 which typically are about 5 inches long, have serrations 28 on the sides thereof which are one thirty-second inch in depth and of a packing density of about 16 grooves per inch.

Various modifications and alternative implementations of the invention will occur to those versed in the art without departing from the spirit and true scope of the invention. Accordingly, it is not intended to limit the invention by what has been particularly shown and described, except as indicated in the appended claims.

What is claimed is:

l. A conveyor system for transporting a work product through an elongated heat-treating furnace comprising:

support means adapted for alignment with the entrance end of a furnace and for the support and lateral movement of product carriers thereon;

said product carriers each having respective opposite sides with serrations therein formed in a regular array of vertical grooves extending substantially along the full length of said carriers;

first and second counterrotatable resilient gears disposed on respective opposite sides of said support means and each operative to engage the respective serrated sides of a product carrier disposed therebetween in intimate gearcoupling relationship;

means for supplying a row of said product carriers to said resilient gears; said resilient gears each including a multitoothed rigid gear mounted on and rotatable with a shaft, a tire of resilient material formed around said rigid gear and in intimate contact with the gear teeth thereof;

means cooperative with said resilient gears and operative to minimize any tendency of said tires to deform upon rotation in gear-coupling relationship with the serrated sides of said product carriers; and

means for driving said resilient gears in counterrotation.

2. A conveyor system according to claim I wherein said driving means includes first and second gears each connected for rotation with a respective resilient gear and each being in mesh with the other, said gears being operative to remain in mesh within a predetermined variation in distance between gear centers.

3. A conveyor system according to claim 1 wherein said cooperative means includes one or more rollers disposed in rolling contact with each of said resilient gears and disposed near the region of product carrier engagement and rearward of the direction of rotation, said rollers being operative to lessen any tendency of said tires to flow or bulge as said resilient gears rotate.

5. A conveyor system according to claim 3 wherein said supplying means includes an inclined track disposed in juxtaposition with said support means and operative to transport said row of product carriers into operative association with said resilient gears. 

1. A conveyor system for transporting a work product through an elongated heat-treating furnace comprising: support means adapted for alignment with the entrance end of a furnace and for the support and lateral movement of product carriers thereon; said product carriers each having respective opposite sides with serrations therein formed in a regular array of vertical grooves extending substantially along the full length of said carriers; first and second counterrotatable resilient gears disposed on respective opposite sides of said support means and each operative to engage the respective serrated sides of a product carrier disposed therebetween in intimate gear-coupling relationship; means for supplying a row of said product carriers to said resilient gears; said resilient gears each including a multitoothed rigid gear mounted on and rotatable with a shaft, a tire of resilient material formed around said rigid gear and in intimate contact with the gear teeth thereof; means cooperative with said resilient gears and operative to minimize any tendency of said tires to deform upon rotation in gear-coupling relationship with the serrated sides of said product carriers; and means for driving said resilient gears in counterrotation.
 2. A conveyor system according to claim 1 wherein said driving means includes first and second gears each connected for rotation with a respective resilient gear and each being in mesh with the other, said gears being operative to remain in mesh within a predetermined variation in distance between gear centers.
 3. A conveyor system according to claim 1 wherein said cooperative means includes one or more rollers disposed in rolling contact with each of said resilient gears and disposed near the region of product carrier engagement and rearward of the direction of rotation, said rollers being operative to lessen any tendency of said tires to flow or bulge as said resilient gears rotate.
 4. A conveyor system according to claim 1 wherein said cooperative means includes a band encircling each of said resilient gears except in the region of product carrier engagement and operative to lessen any tendency of said tires to flow or bulge as said resilient gears rotate.
 5. A conveyor system according to claim 3 wherein said supplying means includes an inclined track disposed in juxtaposition with said support means and operative to transport said row of product carriers into operative association with said resilient gears. 